Apparatus and method for earth drilling



Jan. 25, 1966 J. M. CLEARY 3,231,031

APPARATUS AND METHOD FOR EARTH DRILLING Filed June 18, 1963 N a u i 0 w/ m) g I S:

F lg. 1 INVENTOR.

James M. Cleary ATTEST Attorney United States Patent 1, 31 APPARATUS AN METHOD FOR EARTH DRILLING James M; Cleary, Dallas, Tex., assignor to The Atlantic Refining Company, Philadelphia, Pa, a corporation of Pennsylvania j p Filed June 18, 1963, Ser. No. 238,730 7 Claims. (Cl. 175-67) The present invention is concerned with earth borehole drilling, and more particularly, with a method and apparatus for earth bore-hole drilling wherein there is eroded a pilot hole and sections of the formation between the pilot hole and earth borehole are removed by hydrostatic pressure propagated fractures.

One conventional method of drilling earth boreholes involves the use of a rotary drill bit mounted on the end of a hollow drill string which extends down the borehole from the grounds surface. The drill string is rotated at the earths surface and this rotary motion is transmitted to the drill bit by way of the drill string. The earth cuttings removed by the bit are circulated out of the borehole by pumping a drilling liquid downward- 1y through the drill string and openings in the bit and upwardly in the annulus between the drill string and the borehole. Primarily, to prevent plugging of the outlet openings of the bit and to increase the washing action of the drilling liquid, it became common practice to replace the openings in the bit with nozzles. It was later decided that drilling rate of the bit might be improved if an abrasive material was added to the drilling liquid and the jets (from these nozzles used to abrade, peen, chip and cut the formation. This in turn led to attempts to invent an efficient drilling tool that used only abrasive materials to out the formation.

One object of this invention is to provide an earth borehole drilling method and apparatus which utilizes a single jet stream .in a novel, highly efficient manner to drill an earth borehole. Such a drilling system does not require expensive rotary drive mechanisms used in conventional rotary drilling systems.

Another object of this invention is to provide a novel jet erosion drilling tool which is employed with a rotary drill bit to produce as a unitary result the drilling of a single borehole with greater speed and efficiency than can be obtained by either tool by itself.

Still another object of this invention is to provide a combination drilling system wherein drilling of the borehole is alternated between a rotary drill bit and a jet erosion drilling tool with the drill bit being used some ofthe time and the jet erosion drilling tool used at other times to speed and reduce the cost of drilling through a series of different formations.

These and other objects and advantages of this invention will become apparent in the following description when read in conjunction with the accompanying drawings, in which:

FIGURE 1 is a diagrammatic view partially in section showing ahigh pressure source of drilling liquid, a drill string, a drill collar, a drill bit and pilot member placed in operational position in a subterranean borehole;

FIGURE 2 is a partial longitudinal sectional view of a pilot member and part of a drill collar; and

FIGURE 3 is a transverse view taken along the line 3-3' of FIGURE 2.

This invention utilizes the energy contained in a jet stream of abrasive laden liquid to erode a pilot hole in the bottom of a borehole. Flow of liquid from the pilot hole is restricted and momentarily interrupted causing the energy in the flowing stream to exert a water hammer effect on the lower end of the drill string and on ice the formation between the pilot hole and borehole, thereby causing that part of the formation intermediate the pilot hole and borehole to fracture and separate from the rest of the formation. The separated segments of the [formation thus loosened are broken up and carried off by the jet stream. A new pilot hole is formed and the sequence of events is repeated.

Referring now to the drawings and specifically to FIGURE 1, one embodiment of the invention is shown in drilling position in the borehole wherein the conventional rotary earth drilling arrangement is comprised of high pressure pump 11 which is a pump capable of delivering abrasive laden liquid at a pressure high enough to effect the results hereinafter set forth, which pressure will normally exceed 3000 pounds per square inch and which liquid is pumped into inlet conduit 13 which is connected to swivel head 15 by which hollow drill string 17 is raised and lowered into subterranean borehole 1& The drill string is a substantially rig'id flow conduit extending downwardly from the earths surface into the borehole and receives high pressure abrasive laden liquid from pump 11 by way of inlet conduit 13 and swivel head 15. The drill string is rotated by rotary drive table 21.

The lower end of the drill string is connected to drill collar 23 which is provided with flow passage 25 therethrough having a cross-sectional area of flow at least as large as that through the drill string. The length, L, of the drill collar should be at least twenty feet and the ratio of the outside diameter Olf the drill collar to the diameter of the borehole, d/D, should at least be 0.9. V

The drill collar is connected to bit 27 which is any sort of rotary drill bitsuited for rotary drilling and also provided with a flow passage of at least the same size as the drill string. The drill collar and bit are connected in any standard fashion. As shown, for convenience, the bit is screwed into the lower end of the drill collar.

Extending below the bit is substantially cylindrical pilot noz'zle member 29 hereinafter referred to as the pilot member or nozzle. The pilot member is rigidly connected to the drill bit or drill collars in any suitable fashion, and as shownin FIGURE 1, the upper end of pilot member 259 is threaded and is screwed into bit 27. The pilot member is coaxially aligned with the longitudinal axis of the drill string and drill collar. The pilot member is sturdy enough to withstand without material deformation forces applied to the end thereof of at least 60,000 pounds per square inch of cross-sectional area, and greater. The outside diameter of the pilot member is substantially smaller than the diameter of the borehole cut by the drill bit and substantially smaller than the outside diameter of the drill collar above the pilot. Centrally traversing the length of the pilot member is convergent nozzle passage 31 which directs and focuses a jet stream of the abrasive laden liquid issuing therefrom against the bottom of the borehole ahead of the pilot member. The nozzle has a sufficient-cross-sectional area of flow to allow the (abrasive laden liquid to reach a predetermined flow velocity sufiicient to carry out the purposes hereinafter made apparent and to flush cuttings from the borehole. The diameter of the outlet of the nozzle is substantially less than the outside diameter of the lower end of the pilot member and generally will be less than one-half the outside diameter of the rim of the lower end of the pilot member. The inlet to the nozzle will provide a cross-sectional area of flow sub.-' stantially less than the cross-sectional area of flow of the flow passage which extends through the drill string, drill collar and drill bit.

T! Referring now to FIGURE 2, there is shown a similar drilling system as that shown in FIGURE 1 except for the fact that the drill bit and rotary table are no longer needed.v FIGURE 2.is an enlarged section of the lower end of the drilling system illustrating a system wherein the borehole is drilled solely by the jet erosion drilling tool of this invention. As shown in FIGURE 2, pilot member 29' is screwed into the lower end of drill collar .23 so that the pilot member is rigidly connected thereto.

The pilot and drill collar system of FIGURE 2 is best suited for use in extending an existing borehole. In FIGURE 3, the relationship between the diameter of the outlet of the nozzle passage and the outside diameter of the end of the pilot member is shown. As shown, and

.as stated previously, the outlet of nozzle passage 31 has a diameter less than one-half the diameter of the end of the pilot member. It should also be noted that in FIGURE 3 the periphery of pilot member 29 nearest the walls of the borehole is equipped with arcuate cutout portions 33 which provide flow passages for the drilling particles and liquid are accelerated to form a high velocity unitary jet stream which is jetted from the nozzle and impinges against the bottom of the well bore. The high kinetic energy of the jet stream erodes a pilot hole in the approximate center of the bottom of the borehole when the jet stream impinges against the formation. Parts of the formation cut from the bottom of the pilot hole are very quickly removed from the pilot hole .by the high velocity jet stream so as to not interfere with the drilling efficiency and cutting action of the jet. These particles are carried upward to the earths surface by way of the restricted annulus between the drill collar and the walls of the borehole, and by way of the enlarged annulus between the drill string and borehole walls. The operator lowers the drill string in increments at a rate sufiicient to cause the pilot member to enter the pilot hole and restrict fiow of the drilling liquid from the pilot hole. As the pilotmember enters the pilot hole, the restriction in flow 'of the liquid increases rapidly until flow is essentially completely cut off. The pump, however, continues to supply high pressure liquid to the upper end of the drill string at a fairly constant rate and pressure andthe operator maintains the pressure of the abrasive laden liquid at a level suificient to fracture the earth formation at the bottom of the borehole between the pilot hole and borehole when flow of the liquid from the pilot hole is rapidly interrupted. As stated, the rate of change in the rate of liquid flow is rapid. There is a large amount of energy change when the rate of liquid flow is suddenly reduced from a maximum rate to almost zero. This large amount of energy change creates a water hammer effect which results in two rapidly and almost simultaneously occurring phenomena. First, as the pilot member :moves downard into the pilot hole restricting flow of the liquid from the pilot hole and nozzle, there is a quick increase in hydraulic pressure in the drill collar and a sharp decrease in pressure exterior of the drill collar. These pressure changes cause rapid elastic elongation of the drill string, thus rapidly increasing the downward force of the drill string on the pilot member causing the rim of the lower end of the pilot member to impact against the walls of the pilot hole initiating outwardly extending pancake-like cracks in the formation and completely shutting off flow of liquid from the pilot hole. Second, at almost the same time that the pilot member is impacted against the formation, there is a rapid build-up of pressure in the sealed pilot hole and a rapid decrease in pressure at the bottom of the borehole surrounding the sealed pilot hole. There is, therefore,

a large pressure differential between the inside of the pilot hole and the borehole immediately above the pilot hole. This pressure difference is sufficient to fracture the formation intermediate the pilot hole and borehole. Fracturing of this part of the formation is facilitated by the downward force of the pilot member which also initiates and directs the hydraulic fractures caused by the large pressure differential. The fractures quickly propagate upward to the walls of the borehole thereby separating this part of the formation from the remainder of the formation. When the fracture breaks through, the pressure of the liquid in the drill collar and pilot hole return to normal as the rate of flow from the nozzle resumes unrestricted. The drill string quickly elastically recovers its original length lifting the pilot member above the separated formation fragments loosened by the fracturing pressure and the jet stream breaks up these fragments which are flushed from the borehole by the flowing liquid stream. The jet stream once more erodes a centraily located pilot hole and by lowering the drill string in increments the pilot member again enters the pilot hole repeating the above sequence of events.

From the above description of how the pilot member of this invention is used to carry out a new drilling method wherein a unitary jet of abrasive laden liquid is employed to drill an earth borehole, it should be apparent how this same type of pilot member is especially suited for use with a rotary drill bit to combine the drilling action of both members.

The principles and structures of this invention may be used over a wide variation in type of abrasive laden liquid velocities and liquid pressures. In a typical situation, the diameter of the borehole will be 6 inches, the outside diameter of the drill collar 5.5 inches for a distance of at least 20 feet, the diameter of the flow passage above the nozzle 4.5 inches, the volume rate of flow of 0.5 cubic feet per second, the drilling fluid 70 pounds per cubic foot and the pressure drop across the nozzle 3000 pounds per square inch.

While this invention has been described in connection with certain specific embodiments, the principle involved is susceptible of numerous other applications that will readily occur to persons skilled in the art. The invention is, therefore, to be limited only as indicated by the scope of the appended claims.

Having thus described the various features of the invention,

I claim:

1 An apparatus for earth formation borehole drilling comprising a substantially cylindrical rigid pressure tight unrestricted flow conduit having an upper and lower end and being longer than the length of said borehole, said upper end of said flow conduit connected at the earths surface to a source of liquid under pressure, an earth drilling means near said lower end of said flow conduit and adapted to drill a cylindrical borehole in said formation surrounding said flow conduit, a pilot-like nozzle member extending below said drilling means in coaxial alignment with said flow conduit and having an outside diameter substantially smaller than the diameter of said borehole cut by said drilling means, said pilot-like nozzle member having a circular cross section, said pilot-like nozzle 7 member being a single convergent nozzle passage being centrally located in said pilot-like nozzle member and adapted to direct and focus a jet stream of fluid issuing therefrom against the bottom of said borehole ahead of said pilot-like nozzle member, said convergent nozzle passage forming a solitary outlet to said lower end of said flow conduit, said outlet being less than one-half the outside diameter of the lower end of said pilot member, and the ratio of the outside diameter of said flow conduit to the diameter of said borehole being at least 0.9 for a distance of at least twenty feet immediately above said pilotlike nozzle member.

2. A method for drilling an earth borehole comprising establishing a first flow passage from the earths surface to the formation to be drilled and a second flow passage from the formation to be drilled to the earths surface, the lower end of said first flow passage being surrounded by a rotary drill and terminating in a solitary pilot-like convergent nozzle having a solitary nozzle passage therethrough which communicates with said second fiow passage, at least the lower twenty feet of said second flow passage having a smaller cross-sectional area of flow than the remainder of said second flow passage, rotating said first flow passage to drill a borehole, pumping an abrasiveladen liquid under pressure into said first flow passage at the earths surface thereby forcing a unitary jet of said liquid to issue from said nozzle passage and erode a pilot hole in the bottom of said borehole, lowering said pilotlike convergent nozzle at a rate to maintain said pilot hole smaller than said borehole and to maintain the crosssectional area of said jet at a value less than the crosssectional area of the lower end of said pilot-like convergent nozzle, continuing to lower said pilot-like convergent nozzle whereby said pilot-like convergent nozzle enters said pilot hole and restricts the flow of said liquid from said pilot hole, maintaining the pressure of said liquid in said first flow passage at a level sufiicient to fracture the section of said earth formation between said bottom of said borehole and said pilot hole when flow of said liquid from said pilot hole is rapidly interrupted, and thereafter lowering said pilot-like convergent nozzle to a point whereby said pilot-like convergent nozzle contacts the walls of said pilot hole and the flow of said liquid from said pilot hole is rapidly interrupted thereby causing fracturing of said section of said earth formation.

3. The method of claim 2 wherein the pressure of the abrasive-laden liquid at the earths surface is maintained at a pressure greater than 3000 pounds per square inch.

4. The method of claim 2 wherein the pilot-like convergent nozzle is lowered at a rate to maintain the crosssectional area of the jet at a value less than one-half the cross-sectional area of the lower end of said pilot-like convergent nozzle.

5. The method of claim 2 wherein the method in addition includes the step of periodically impacting said pilotlike convergent nozzle against the walls of the pilot hole.

6. The method of claim 3 wherein the volume rate of flow of the abrasive-laden fluid at the earths surface is at least 0.5 cubic foot per second.

7. The method of claim 6 wherein the pilot-like convergent nozzle is lowered at a rate to maintain the crosssectional area of the jet at a value less than one-half the cross-sectional area of the lower end of said pilot-like convergent nozzle.

References Cited by the Examiner UNITED STATES PATENTS 243,015 6/1881 Vaughn et al -422 X 1,831,209 11/1931 Thornley et a1. 175422 X 2,963,102. 12/1960 Smith 175422 X 3,081,828 3/1963 Quick 175-67 CHARLES E. OCONNELL, Primary Examiner.

BENJAMIN B. BENDETT, Examiner. 

1. AN APPARATUS FOR EARTH FORMATION BOREHOLE DRILLING COMPRISING A SUBSTANTIALLY CYLINDRICAL RIGID PRESSURE TIGHT UNRESTRICTED FLOW CONDUIT HAVING AN UPPER AND LOWER END AND BEING LONGER THAN THE LENGTH OF SAID BOREHOLE, SAID UPPER END OF SAID FLOW CONDUIT CONNECTED AT THE EARTH''S SURFACE TO A SOURCE OF LIQUID UNDER PRESSURE, AN EARTH DRILLING MEANS NEAR SAID LOWER END OF SAID FLOW CONDUIT AND ADAPTED TO DRILL A CYLINDRICAL BOREHOLE IN SAID FORMATION SURROUNDING SAID FLOW CONDUIT, A PILOT-LIKE NOZZLE MEMBER EXTENDING BELOW SAID DRILLING MEANS IN COAXIAL ALIGNMENT WITH SAID FLOW CONDUIT AND HAVING AN OUTSIDE DIAMETER SUBSTANTIALLY SMALLER THAN THE DIAMETER OF SAID BOREHOLE CUT BY SAID DRILLING MEANS, SAID PILOT-LIKE NOZZLE MEMBER HAVING A CIRCULAR CROSS SECTION, SAID PILOT-LIKE NOZZLE MEMBER BEING A SINGLE CONVERGENT NOZZLE MEMBER AND CENTRALLY LOCATED IN SAID PILOT-LIKE NOZZLE MEMBER AND ADAPTED TO DIRECT AND FOCUS A JET STREAM OF FLUID ISSUING THEREFROM AGAINST THE BOTTOM OF SAID BOREHOLE AHEAD OF SAID PILOT-LIKE NOZZLE MEMBER, SAID CONVERGENT NOZZLE PASSAGE FORMING A SOLITARY OUTLET TO SAID LOWER END OF SAID FLOW CONDUIT, SAID OUTLET BEING LESS THAN ONE-HALF THE OUTSIDE DIAMETER OF THE LOWER END OF SAID PILOT MEMBER, AND THE RATIO OF THE OUTSIDE DIAMETER OF SAID FLOW CONDUIT TO THE DIAMETER OF SAID BOREHOLE BEING AT LEAST 0.9 FOR A DISTANCE OF AT LEAST TWENTY FEET IMMEDIATELY ABOVE SAID PILOTLIKE NOZZLE MEMBER.
 2. A METHOD FOR DRILLING AN EARTH BOREHOLE COMPRISING ESTABLISHING A FIRST FLOW PASSAGE FROM THE EARTH''S SURFACE 